The patch titled Subject: mm/z3fold.c: fix z3fold_destroy_pool() race condition has been added to the -mm tree. Its filename is mm-z3foldc-fix-z3fold_destroy_pool-race-condition.patch

This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/mm-z3foldc-fix-z3fold_destroy_pool-... and later at http://ozlabs.org/~akpm/mmotm/broken-out/mm-z3foldc-fix-z3fold_destroy_pool-...

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------------------------------------------------------ From: Henry Burns henryburns@google.com Subject: mm/z3fold.c: fix z3fold_destroy_pool() race condition

The constraint from the zpool use of z3fold_destroy_pool() is there are no outstanding handles to memory (so no active allocations), but it is possible for there to be outstanding work on either of the two wqs in the pool.

Calling z3fold_deregister_migration() before the workqueues are drained means that there can be allocated pages referencing a freed inode, causing any thread in compaction to be able to trip over the bad pointer in PageMovable().

Link: http://lkml.kernel.org/r/20190726224810.79660-2-henryburns@google.com Fixes: 1f862989b04a ("mm/z3fold.c: support page migration") Signed-off-by: Henry Burns henryburns@google.com Cc: Vitaly Vul vitaly.vul@sony.com Cc: Vitaly Wool vitalywool@gmail.com Cc: Shakeel Butt shakeelb@google.com Cc: Jonathan Adams jwadams@google.com Cc: David Howells dhowells@redhat.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Al Viro <viro@zeniv.linux.org.uk Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/z3fold.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/mm/z3fold.c~mm-z3foldc-fix-z3fold_destroy_pool-race-condition +++ a/mm/z3fold.c @@ -817,16 +817,19 @@ out: static void z3fold_destroy_pool(struct z3fold_pool *pool) { kmem_cache_destroy(pool->c_handle); - z3fold_unregister_migration(pool);

/* * We need to destroy pool->compact_wq before pool->release_wq, * as any pending work on pool->compact_wq will call * queue_work(pool->release_wq, &pool->work). + * + * There are still outstanding pages until both workqueues are drained, + * so we cannot unregister migration until then. */

destroy_workqueue(pool->compact_wq); destroy_workqueue(pool->release_wq); + z3fold_unregister_migration(pool); kfree(pool); }

_

Patches currently in -mm which might be from henryburns@google.com are

mm-z3foldc-fix-z3fold_destroy_pool-ordering.patch mm-z3foldc-fix-z3fold_destroy_pool-race-condition.patch